The trick, the team explains, involves silica nanoparticles, spray-applied to the plastic surface using a solvent. The substance in the bottle can’t get a grip on the plastic surface, because the silica particles are guarding it. The soap can’t seep between the particles, and air pockets form between them, underneath the soap—that’s what keeps the soap moving along.

It’s nice for consumers, and might save them a few bucks, but it’s also big business: “Manufacturers are really interested in this, because they make billions of bottles that end up in the garbage with product still in them,” said Bhushan, a professor of mechanical engineering at Ohio State.

The coating is designed specifically to work on polypropylene, known in the United States as “number 5” plastic.

From Food to Soap

Other products have addressed the same problem in different ways. A nonstick nanocoating barrier for food applications was developed at Massachusetts Institute of Technology in 2012 and hit the consumer market last year, promising to let you get ketchup out of the bottle more easily. That substance has been licensed for use in food products in Europe.

The soap issue is a stickier subject, though.

“Compared to soaps, getting ketchup out of a bottle is trivial,” Bhushan says. “Our coating repels liquids in general, but getting it to repel soap was the hard part.”